A mystery...

This one is a mystery to me. The parent cordon of both these fruit is Dr Jules Guyot. I remember budding Devoe onto one half of the Y when my husband broke the original maiden graft by mistake, and I had to take rapid action not to lose the variety. However, there is a section between Dr Jules and the Devoe extention production very nice but quite alien fruit. I have no memory of budding anything else on, and the fruit is unlike anything else I grow (superficially a little like Comice, but about half the size). I can't see any scars at the base of the spur that would suggest it had been budded, or grafted further back, whereas the scars are still very obvious where the Devoe spurs were added. Could it be a bud sport ?